At the present time, it is customary to pack various perishable products in flexible bags or pouches of plastic having an attached spout with which a removable and replaceable cap cooperates, the filling of the bag usually being accomplished after removing the cap which is then replaced to seal the bag. The plastic bag is usually made of a polylaminate which includes a barrier film composite that prevents the permeation of gases, especially oxygen, which would tend to spoil the contents. However, although the bag material itself has included the gas barrier, there is gas penetration through the spout and cap assembly within the seal between the external flange of the spout and bag and even through the spout and cap material itself which is usually of polyethylene but may be of other plastics. It is not uncommon for the permeation rate through the spout and cap assembly to be six times the rate of permeation through the entire remaining surface area of a four liter bag or pouch.
The present invention substantially reduces the penetration of oxygen or other gases through the spout and cap assembly by providing a barrier film or coating to the flange of the spout from where it is sealed to the bag and inwardly to a point overlapping a cooperating barrier film extending transversely completely across the cap. However, the arrangement is such that the cap is removable for filling and can then be replaced to become in combination with the spout substantially an impermeable assembly.